This invention relates in general to self-supporting, temporary shelters having a forcefully foldable frame made entirely of separate resilient wire loops, having an envelope which encloses at least a portion of a volume defined by the frame, and having a balancing of tensile forces between the frame and the envelope by which the form of the shelter is achieved.
U.S. Pat. No. 4,858,634 by McLeese presents a self-erecting tent structure having an elliptical base loop and at least a second loop formed in the shape of a saddle clamped to the base loop, the high ends of the saddle providing arches for vertical support. This structure is illustrated in FIG. 22. The patent discloses that the low ends of the saddle loop are attached to the base loop at at least two points. FIG. 22 illustrates that the saddle is attached to the base loop at at least four points, two on each side. There are several disadvantages to this configuration. In practice, the clamps attaching the saddle loop to the base loop have tremendous forces exerted against them when the structure is folded. These tremendous forces almost invariably release the clamps causing dis-attachment of the saddle loop from the base loop. Moreover, the memories of the loops do not apply tension to the fabric comprising the sides of the tent because there are no opposing forces between the saddle loop and the base loop, so the sides tend to sag.
U.S. Pat. No. 5,163,461 by Ivanovich et al., discloses another self-erecting structure but in this case the framework is made from a single loop folded in various ways to provide a footing and vertical support arches. FIG. 1 illustrates a shelter in which the single loop is folded so as to have an elliptical base and a saddle-shaped superstructure. However, this configuration has several disadvantages. The forces applied by the memory of the loop are asymmetrical due to differences in how the superstructure and the base loop come together at the front and back of the structure. At the front, there is a crossing of the loop's wire whereas at the back, the saddle dips down to meet the base loop and is clamped to the base loop. Because of this arrangement, the memory in the superstructure tends to drive the back end of the saddle downward past the base loop, and that is apparently why clamping is necessary. Thus, at the back of the structure, there is no lifting tension on the covering fabric and so the fabric near the juncture of the back end of the saddle and the base loop tends to sag. If the tent has a fabric flood barrier around its base, as most tents do, this sagging tends to lower the height of the flood barrier with obviously disadvantageous results. This sagging is even more so when the clamping between the saddle and the base becomes disengaged, as it easily can because of the large forces applied to the clamps during folding. Another disadvantage is that the connector which couples the ends of the loop's wire together to close the loop is located and exposed at the entrance of the structure. (See FIG. 3, item 5). If a wire end becomes disengaged from the connector, it can create a hazardous condition.
As will be more fully explained in the description of the preferred embodiment, this invention uses two independent, resilient wire loops to impart more uniform and symmetrical tensile forces to the envelope, typically fabric, to keep it taut, including the lower rim of the envelope where a flood barrier is typically located. Moreover, the cost of manufacturing and maintenance of such shelters is reduced because of, among other things, the lack of any need to clamp the loops together.
Other advantages and attributes of this invention will be readily discernable upon a reading of the text hereinafter.